Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $56.99   9.695%   $62.5152   $62.52   $62.50   $62.50  
  Purchase #2 $187.78   3.833%   $194.9776   $194.98   $195.00   $195.00  
  Purchase #3 $51.99   10.842%   $57.6268   $57.63   $57.65   $57.60  
  Purchase #4 $194.85   9.232%   $212.8386   $212.84   $212.85   $212.80  
  Purchase #5 $21.69   13.373%   $24.5906   $24.59   $24.60   $24.60  
  Purchase #6 $189.56   10.261%   $209.0108   $209.01   $209.00   $209.00  
  Purchase #7 $176.27   6.683%   $188.0501   $188.05   $188.05   $188.10  
  7 purchase totals = $879.13       $949.6097   $949.62   $949.65   $949.60